<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>延伸</title>
    <style>
        div{
            width:100px;
            height:100px;
            background:yellow;
            transition:width 1s;
            line-height: 100px;
            text-align: center;
        }
        div:hover{
            width:100%;
            text-align: center;
            font-size: 24px;
        }
    </style>
</head>
<body>
<div>马建蕾</div>
</body>
</html>